Bone marrow stromal antigen 2 (BST2, also known as tetherin or CD317) is an interferon-inducible antiviral factor which restricts the release of diverse mammalian enveloped viruses by tethering nascent virions at the plasma membrane (Wang SM et al. 2014, 2019; Taylor JK et al. 2015; Perez-Caballero D et al. 2009). BST2 functions as a disulfide-linked homodimer (Andrew AJ et al. 2009; Wang SM et al. 2014). BST2 restricts the release of viruses that bud at the plasma membrane or intracellular compartments. Specifically, coronaviruses bud in the ER-Golgi apparatus intermediate compartment (ERGIC) and then released from the cell via vesicle fusion. In human cells, BST2 inhibited the release of human coronavirus 229E (hCoV-229E) and severe acute respiratory syndrome coronavirus type 1 (SARS-CoV-1) (Wang SM et al. 2014, 2019; Taylor JK et al. 2015). Many viruses have evolved antagonists to counteract BST2 antiviral activity. Coimmunoprecipitation experiments showed that the transmembrane protein SARS‐CoV-1 ORF7a (7a) interacted with BST2 upon co-expression in human embryonic kidney 293 (HEK293) cells (Taylor JK et al. 2015). Cellular localization studies revealed that 7a, an ERGIC resident viral protein, co-localized with BST2 at the plasma membrane upon co-expression in HEK293T cells (Taylor JK et al. 2015). The viral 7a protein reduced the tethering function of BST2 by interfering with BST2 glycosylation (Taylor JK et al. 2015).

This Reactome event shows binding of SARS-CoV-1 7a to host BST2 thus disrupting the antiviral effect of BST2.